Device for injecting aqueous additives in a motor vehicle exhaust pipe

ABSTRACT

This invention relates to a device for injecting aqueous additives into an exhaust pipe of a motor vehicle, including an additive tank and a pumping module for taking the additive and directing it toward the exhaust pipe, characterized in that the pumping module includes a rotary electric pump ( 120 ) and includes a thermally conductive part ( 170 ) in contact with the casing of the pump ( 120 ) and the outlet of a pressure regulator ( 150 ) so as to transfer heat to said outlet of the pressure regulator ( 150 ).

This invention relates to the field of motor vehicle exhaust pipes.

More specifically, this invention relates to a device for nitrogen oxide treatment by catalytic reduction using aqueous additives, for example a urea solution, injected into or upstream of a catalyst.

Such treatment devices, as shown in the appended FIG. 1, have already been proposed for many years.

This FIG. 1 shows a device that includes:

-   -   an exhaust pipe 1 including a catalyst 2,     -   a tank 3 for additive, for example a urea solution, and     -   a module 10 intended to take additive from the tank 3 in order         to inject it into the exhaust pipe 1 by a supply line 11 and an         injector 12.

The devices of the type shown in FIG. 1 have already provided useful services.

At high temperature, urea decomposes into ammonia and carbon gas.

Ammonia reacts in turn with nitrogen oxides in order to form nitrogen and water.

However, they do not always provide total satisfaction.

In particular, the known devices are often subject to malfunction at very low temperature, in particular when the urea solution injection devices are equipped with a pressure regulator.

This invention is intended to improve the known devices so as to eliminate the malfunctions observed.

This objective is achieved by the invention, owing to a device for injecting an aqueous additive into an exhaust pipe of a motor vehicle, including an additive tank and a pumping module for taking the additive and directing it toward the exhaust pipe, characterized in that the pumping module includes a rotary electric pump and includes a thermally conductive part in contact with the casing of the pump and the outlet of a pressure regulator so as to transfer heat to said outlet of the pressure regulator.

According to an advantageous feature of this invention, the part in contact with the casing of the pump and the outlet of the pressure regulator in order to transfer heat to said outlet of the pressure regulator is a thermally conductive part.

A person skilled in the art will understand that the structure proposed in this invention makes it possible to warm up the outlet of the pressure regulator and thus eliminate malfunctions due to freezing of the aqueous additive at the outlet of the pressure regulator, which the applicant identified as one of the major sources of malfunctions.

Other features, objectives and advantages of the present invention will appear in the following detailed description, and in view of the appended drawings, provided as non-limiting examples, in which:

FIG. 1 described above diagrammatically shows a system according to the prior art designed for injecting a urea solution in a motor vehicle exhaust pipe,

FIG. 2 diagrammatically shows a module for injecting additives according to this invention,

FIG. 3 diagrammatically shows a module for injecting additives according to an alternative of this invention, and

FIG. 4 diagrammatically shows a module for injecting additives according to another alternative of this invention.

The appended FIG. 2 shows a module 100 according to this invention including a base 110 intended to be attached to the upper wall of an additive tank and which has a rotary electric pump 120 and a pressure regulator 150.

The rotary electric pump 120 and the pressure regulator 150 can be the subject of numerous alternative embodiments known to a person skilled in the art. Therefore, they will not be described in detail below.

Preferably, however, in this invention, the rotary electric pump 120 is a pump comprised of two separate parts: an electrical control part 122 and a mechanical pumping part 130. The electrical, control part 122 preferably includes an external wound stator 123 suitable for generating, when there is an adequate electric power supply, a rotating electric field making it possible to rotate a rotor associated with a shaft 125.

The electrical control part 122 and the mechanical pumping part 130 are preferably separated by a sealed partition 140.

The use of an electric pump including two compartments, one for electrical control and the other for pumping mechanics, separated by a sealed partition 140, makes it possible to prevent possible leakages of additives toward the electric winding.

The transmission of the rotation movement between the rotor of the electrical control part 122 and an element opposite the mechanical pumping part 130 is achieved by means of permanent magnets or any equivalent means, one 126 secured to the shaft 125 on the side of the wall 140 located in the chamber housing the electrical control part 122 and the other 136 located opposite, on the other side of the sealed wall 140, in the chamber housing the mechanical pumping part 130.

The mechanical pumping part 130 can be the subject of numerous embodiments. It is preferably a gear system of which the inlet shaft is rotatably mounted about an axis O-O aligned with the axis of the rotor 125.

The electrical pump 120 is preferably a brush-free pump.

The regulator 150 preferably includes, as shown in FIG. 3, a casing 152 divided into two chambers 153, 155 by a membrane 156.

A first chamber 155 communicates with the outlet 131 of the mechanical pumping part 130, by any suitable means, for example by means of a tubular line 142.

The second chamber 153 of the pressure regulator 150 houses a calibrated spring 152 that urges said membrane 156 against a valve 157 located in the first chamber 155, of which the outlet communicates with a conduit 160 forming an additive return, which leads to the base of the tank receiving the module 100.

Insofar as the pressure delivered by the outlet of the pump 120 is lower than the force applied to the membrane 156 by the calibrated spring 154, the membrane 156 is applied against the valve 157 and no additive is delivered by the outlet conduit 160.

Instead, when the outlet pressure of the mechanical pumping part 130 exceeds the calibration force of the spring 154, the membrane 156 is detached from the valve 157. Consequently, the excess pressure of additives delivered by the pump 100 is sent to the additive tank by means of the conduit 160.

As indicated above, according to an essential feature of the invention, the module also includes a thermally conductive part 170 in contact with the casing of the pump, more specifically the casing portion surrounding the electrical control module 122, and in contact with the outlet of the pressure regulator 150. The part 170 thus makes it possible to transfer heat from the electrical control part 122 to the outlet of the pressure regulator 150.

The part 170 thus makes it possible to warm up and melt, if necessary, any mass of additives capable of obstructing the outlet of the pressure regulator at low temperature.

The thermally conductive metal part 170 is preferably made of brass or stainless steel.

According to another advantageous feature of this inventive, timing means are preferably provided, which are suitable for supplying power, in an initial phase, and during a determined period, for example but not limited to approximately 20 minutes, to the electrical control module 122 in a state so that it does not generate a rotating field capable of causing the mechanical pumping part 130 to rotate, but acts as an electrically resistive winding capable of releasing heat by Joule effect, enabling the pressure regulator 150 to be warmed up by means of the metal part 170.

The timed device ensuring control of the electrical power supply of the engine when the vehicle is started so as to heat the winding without causing the pump to rotate is controlled by a measurement of the temperature of the urea solution, which performs this control only when the value is near the solidification temperature of the urea solution.

Also more specifically, according to the specific non-limiting embodiment shown in FIG. 2, the metal part 170 is a tubular part centered on the O-O axis of the pump 120 and in contact over a portion of the height thereof, at least at the level of the electrical control part 122, with the casing of the pump 120.

It will be noted in the examination of the appended FIG. 2 that the metal part 170 can he in contact with the casing of the pressure regulator 150 and/or the pump casing only over a portion of the height thereof.

Indeed, there is a space 171 between the tube 170 and the casing of the pressure regulator in order to allow free thermal expansion.

Alternatively, the metal tube 170 is cracked so as to ensure that the tube 170 is kept in contact with the pump body 120 and so as to enable compensation for the play due to thermal expansion.

According to yet another alternative embodiment of this invention, the thermally conductive part 170 is a multilobar tube so as to ensure good thermal contact with the casing of the motor portion of the pump while allowing free dilation and free deformation of said part 170.

The use of such a thermally conductive metal part 170 in contact with the casing of the pump 120 also makes it possible, when necessary, to cool the electrical control part 122.

It will be noted in this regard that the lower portion of the tubular metal part 170 is also in contact with the casing portion surrounding the mechanical pumping part 130 at the level of an internal collar 172.

According to a specific non-limiting embodiment of this invention, the thermally conductive metal part enabling the outlet of the pressure regulator 150 to be warmed up is formed by overmolding the plastic base 110 on said part 170.

Such an embodiment makes it possible to produce the entire module at low cost.

FIG. 3 shows an alternative embodiment, according to which the outlet conduit 160 of the pressure regulator 150 is directly in contact with the casing of the pump 120.

FIG. 4 shows another alternative embodiment, in which the outlet conduit 160 of the pressure regulator 150 is formed by a plastic end piece 162 integral with the base 110 and which has a thermally conductive tubular insert 164, for example made of metal. The end piece 162 has a low thickness so as not to act as a barrier to heat transfer. It is in contact with a metal part 170 that is itself in contact with the casing of the pump motor 122.

Preferably, as shown in FIG. 4, the insert 164 is also in contact with a vertical metal tube 166 that extends the end piece 162 and that is connected to the top portion 202 of a heater 200 associated with a suction filter 210 placed at the inlet of the pump 120.

This heater 200 and this filter 210 are the subject of another patent application filed in parallel by the applicant. Therefore, they will not be described in detail below.

A person skilled in the art will understand that the tube 166 connected to the heater 200 makes it possible to reinforce the warming up of the outlet of the pressure regulator 150 when necessary.

This invention makes it possible to solve the problems encountered in the prior art, including for modules in which he pressure regulator is not purged.

Of course, this invention is not limited to the specific embodiment described above, but includes any alternative consistent with the invention.

This invention in particular is not limited to the use of urea solutions, but applies to the use of all aqueous additives making it possible, by catalytic reduction, to transform nitrogen oxides. 

1. Device for injecting aqueous additives into an exhaust pipe of a motor vehicle, including an additive tank and a pumping module for taking the additive and directing it toward the exhaust pipe, characterized in that the pumping module includes a rotary electric pump (120) and includes a thermally conductive part (170) in contact with a casing of the pump (120) and an outlet of a pressure regulator (150) so as to transfer heat to said outlet of the pressure regulator (150).
 2. Device according to claim 1, characterized in that the part (170) in contact with the casing of the pump (120) and the outlet of the pressure regulator (150) in order to transfer heat to said outlet of the pressure regulator (150) is a thermally conductive part.
 3. Device according to claim 2, characterized in that the thermally conductive part (170) is in contact with a pump casing portion (120) surrounding an electrical control part (122).
 4. Device according to claim 2, characterized in that the thermally conductive part (170) is a longitudinally cracked tube.
 5. Device according to claim 2, characterized in that the thermally conductive part (170) is a multilobar tube.
 6. Device according to claim 1, characterized in that the outlet conduit (160) of the pressure regulator (150) is formed by a plastic end piece (162) in contact with the part (170) ensuring the transfer of heat from the pump casing (120).
 7. Device according to claim 6, characterized in that the outlet conduit (160) of the pressure regulator (150) is integral, with a base (110).
 8. Device according to claim 6, characterized in that the outlet conduit (160) of the pressure regulator (150) has a thermally conductive tubular insert (164).
 9. Device according to claim 1, characterized in that the outlet conduit (160) of the pressure regulator (150) is in contact with a vertical metal tube (166) that is connected to a top portion (202) of a heater (200) associated with a suction filter (210) placed at an inlet of the pump (120).
 10. Device according to claim 1, characterized in that the additive is a urea solution.
 11. Device according to claim 1, characterized in that the pump is a two-part pump including an electrical control part and a mechanical pumping part, which are magnetically coupled.
 12. Device according to claim 1, characterized in that the pump (120) includes an electrical control part (122) with an external stator capable of generating a rotary field.
 13. Device according to claim 1, characterized in that the thermally conductive part (170) is made of brass.
 14. Device according to claim 1, characterized in that the thermally conductive part is in contact with a mechanical pumping part of the pump (130).
 15. Device according to claim 1, characterized in that it includes timed means suitable for ensuring control of the electrical power supply of the engine when the vehicle is started so as to heat a winding of the motor (120) without rotating the pump when a measured temperature of the additive indicates a value close to the solidification temperature. 